Based on kernel version 2.6.39.1. Page generated on 2011-06-03 13:47 EST.

1 __
2 (___()'`; Rusty's Remarkably Unreliable Guide to Lguest
3 /, /` - or, A Young Coder's Illustrated Hypervisor
4 \\"--\\ http://lguest.ozlabs.org56Lguest is designed to be a minimal 32-bit x86 hypervisor for the Linux kernel,
7for Linux developers and users to experiment with virtualization with the
8minimum of complexity. Nonetheless, it should have sufficient features to
9make it useful for specific tasks, and, of course, you are encouraged to fork
10and enhance it (see drivers/lguest/README).
1112Features:
1314- Kernel module which runs in a normal kernel.
15- Simple I/O model for communication.
16- Simple program to create new guests.
17- Logo contains cute puppies: http://lguest.ozlabs.org1819Developer features:
2021- Fun to hack on.
22- No ABI: being tied to a specific kernel anyway, you can change anything.
23- Many opportunities for improvement or feature implementation.
2425Running Lguest:
2627- The easiest way to run lguest is to use same kernel as guest and host.
28 You can configure them differently, but usually it's easiest not to.
2930 You will need to configure your kernel with the following options:
3132 "General setup":
33 "Prompt for development and/or incomplete code/drivers" = Y
34 (CONFIG_EXPERIMENTAL=y)
3536 "Processor type and features":
37 "Paravirtualized guest support" = Y
38 "Lguest guest support" = Y
39 "High Memory Support" = off/4GB
40 "Alignment value to which kernel should be aligned" = 0x100000
41 (CONFIG_PARAVIRT=y, CONFIG_LGUEST_GUEST=y, CONFIG_HIGHMEM64G=n and
42 CONFIG_PHYSICAL_ALIGN=0x100000)
4344 "Device Drivers":
45 "Block devices"
46 "Virtio block driver (EXPERIMENTAL)" = M/Y
47 "Network device support"
48 "Universal TUN/TAP device driver support" = M/Y
49 "Virtio network driver (EXPERIMENTAL)" = M/Y
50 (CONFIG_VIRTIO_BLK=m, CONFIG_VIRTIO_NET=m and CONFIG_TUN=m)
5152 "Virtualization"
53 "Linux hypervisor example code" = M/Y
54 (CONFIG_LGUEST=m)
5556- A tool called "lguest" is available in this directory: type "make"
57 to build it. If you didn't build your kernel in-tree, use "make
58 O=<builddir>".
5960- Create or find a root disk image. There are several useful ones
61 around, such as the xm-test tiny root image at
62http://xm-test.xensource.com/ramdisks/initrd-1.1-i386.img6364 For more serious work, I usually use a distribution ISO image and
65 install it under qemu, then make multiple copies:
6667 dd if=/dev/zero of=rootfile bs=1M count=2048
68 qemu -cdrom image.iso -hda rootfile -net user -net nic -boot d
6970 Make sure that you install a getty on /dev/hvc0 if you want to log in on the
71 console!
7273- "modprobe lg" if you built it as a module.
7475- Run an lguest as root:
7677 Documentation/lguest/lguest 64 vmlinux --tunnet=192.168.19.1 --block=rootfile root=/dev/vda
7879 Explanation:
80 64: the amount of memory to use, in MB.
8182 vmlinux: the kernel image found in the top of your build directory. You
83 can also use a standard bzImage.
8485 --tunnet=192.168.19.1: configures a "tap" device for networking with this
86 IP address.
8788 --block=rootfile: a file or block device which becomes /dev/vda
89 inside the guest.
9091 root=/dev/vda: this (and anything else on the command line) are
92 kernel boot parameters.
9394- Configuring networking. I usually have the host masquerade, using
95 "iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE" and "echo 1 >
96 /proc/sys/net/ipv4/ip_forward". In this example, I would configure
97 eth0 inside the guest at 192.168.19.2.
9899 Another method is to bridge the tap device to an external interface
100 using --tunnet=bridge:<bridgename>, and perhaps run dhcp on the guest
101 to obtain an IP address. The bridge needs to be configured first:
102 this option simply adds the tap interface to it.
103104 A simple example on my system:
105106 ifconfig eth0 0.0.0.0
107 brctl addbr lg0
108 ifconfig lg0 up
109 brctl addif lg0 eth0
110 dhclient lg0
111112 Then use --tunnet=bridge:lg0 when launching the guest.
113114 See:
115116http://www.linuxfoundation.org/collaborate/workgroups/networking/bridge117118 for general information on how to get bridging to work.
119120- Random number generation. Using the --rng option will provide a
121 /dev/hwrng in the guest that will read from the host's /dev/random.
122 Use this option in conjunction with rng-tools (see ../hw_random.txt)
123 to provide entropy to the guest kernel's /dev/random.
124125There is a helpful mailing list at http://ozlabs.org/mailman/listinfo/lguest126127Good luck!
128Rusty Russell rusty@rustcorp.com.au.